1. Field of the invention
The present invention relates to turbochargers for internal combustion engines. More particularly, the present invention relates to a turbocharger control system including a main oil supply pump, a first regulated oil circuit operable to variably and selectively supply pressure-regulated oil to bearings of a turbocharger apparatus at a first pressure in order to hydraulically pre-load the bearings, and a second oil circuit operable to variably and selectively supply pressure-regulated oil to other portions of the turbocharger apparatus at a second pressure. The present invention also relates to an engine incorporating the improved turbocharger, and to a method of using the same.
2. Description of the Background Art
There are known turbocharger systems for controlling and operating turbocharger apparatus, which are widely used on internal combustion engines for vehicles. Internal combustion engines equipped with turbochargers generally decrease the overall weight of vehicles in which they are installed, improve performance of the vehicles, and enhance fuel efficiency.
Some examples of turbocharger apparatus are disclosed in drawings 1 and 2 of U.S. Pat. No. 4,387,573, which are reproduced as FIGS. 6 and 7 herein, in order to generally discuss the known functions of turbochargers. The entire disclosure of U.S. Pat. No. 4,387,573 is incorporated herein by reference, as background information regarding known turbocharger systems. The reference numbers used herein regarding FIGS. 6 and 7 are different from the reference numbers used in the original patent.
As shown in FIGS. 6-7, in an internal combustion engine 200, it has been known to divert part of the engine exhaust flowing outwardly through the exhaust manifold 202, to feed such diverted exhaust flow through a turbo feed pipe 204 to a turbocharger 205, and to spin an exhaust turbine wheel 206 of the turbocharger 205 with such exhaust flow received from the internal combustion engine 200. The exhaust turbine wheel 206 is operatively attached to an intake-side turbine wheel 210, for concurrent rotation, via a connecting shaft 208.
Incoming intake air for combustion is compressed by the intake-side turbine wheel 210 to create high-density charge air, which is then routed into the intake manifold of the engine via an intake duct pipe 212, and is combined with fuel for burning inside of the engine 200.
A number of different designs are known for turbochargers. Examples of some of the known turbocharger designs include those described in U.S. Pat. No. 4,652,219 to McEachern, Jr. et al., U.S. Pat. No. 4,676,667 to Komatsu et al., U.S. Pat. No. 4,789,253 to Perego, U.S. Pat. No. 4,798,523 to Glaser et al., U.S. Pat. No. 5,735,676 to Loos, and U.S. Pat. No. 7,371,011 to McKiernan, Jr.
Other patents, on other various known machines having pre-loaded bearings therein, include U.S. Pat. No. 5,051,005 to Duncan, U.S. Pat. No. 5,388,917 to Hibi et al., and U.S. Pat. No. 6,042,273 to Thrasher.
While it has been known, under some circumstances, to use engine oil to hydraulically pre-load turbocharger bearings, the known designs have been limited to using engine oil supplied at the pressure provided by the first oil circuit. Such known designs have drawbacks, since they do not separately and selectively control and regulate pressure applied to turbocharger bearings for achieving pre-loading thereof.
When a turbocharged engine is idling and is relatively cool, it is not always necessary to provide highly pressurized oil to the turbocharger bearings. Indeed, under some circumstances, if oil is provided to the turbocharger bearings at an increased pressure during idling, such pressurized oil may increase the delay or lag time of the turbocharger, and thereby deteriorate engine performance.
Also, it is desired that the bearings are pre-loaded while taking into account operational factors, such as engine speed, turbocharger rotary speed, engine coolant temperature, and intake manifold pressure, for achieving optimal performance of the turbocharger. However, it is the applicant's understanding that conventional turbocharger operating systems do not take such parameters into consideration.
Although the known devices have some utility for their intended purposes, a need still exists in the art for an improved turbocharger operating system and method for variably pre-loading turbocharger bearings. In particular, there is a need for an improved turbocharger operating system and method which will promote extended life of turbocharger bearings, and which will enhance engine performance.
Accordingly, it is one of the objects of the present invention to provide a method and apparatus for turbocharging an internal combustion engine, in which oil pressure applied to turbocharger bearing assemblies is controlled and regulated separately from a main engine oil supply, for variably and selectively controlling hydraulic pre-loading of the turbocharger bearings.
It is another object of the present invention to provide two separate, independently controlled oil circuits for supplying oil at different regulated pressures to different parts of a turbocharger apparatus.